/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.context.request.async;

import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.WebRequest;

import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Utility methods related to processing asynchronous web requests.
 *
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @since 3.2
 */
public abstract class WebAsyncUtils {

    /**
     * The name attribute containing the {@link WebAsyncManager}.
     */
    public static final String WEB_ASYNC_MANAGER_ATTRIBUTE =
            WebAsyncManager.class.getName() + ".WEB_ASYNC_MANAGER";


    /**
     * Obtain the {@link WebAsyncManager} for the current request, or if not
     * found, create and associate it with the request.
     */
    public static WebAsyncManager getAsyncManager(ServletRequest servletRequest) {
        WebAsyncManager asyncManager = null;
        Object asyncManagerAttr = servletRequest.getAttribute(WEB_ASYNC_MANAGER_ATTRIBUTE);
        if (asyncManagerAttr instanceof WebAsyncManager) {
            asyncManager = (WebAsyncManager) asyncManagerAttr;
        }
        if (asyncManager == null) {
            asyncManager = new WebAsyncManager();
            servletRequest.setAttribute(WEB_ASYNC_MANAGER_ATTRIBUTE, asyncManager);
        }
        return asyncManager;
    }

    /**
     * Obtain the {@link WebAsyncManager} for the current request, or if not
     * found, create and associate it with the request.
     */
    public static WebAsyncManager getAsyncManager(WebRequest webRequest) {
        int scope = RequestAttributes.SCOPE_REQUEST;
        WebAsyncManager asyncManager = null;
        Object asyncManagerAttr = webRequest.getAttribute(WEB_ASYNC_MANAGER_ATTRIBUTE, scope);
        if (asyncManagerAttr instanceof WebAsyncManager) {
            asyncManager = (WebAsyncManager) asyncManagerAttr;
        }
        if (asyncManager == null) {
            asyncManager = new WebAsyncManager();
            webRequest.setAttribute(WEB_ASYNC_MANAGER_ATTRIBUTE, asyncManager, scope);
        }
        return asyncManager;
    }

    /**
     * Create an AsyncWebRequest instance. By default, an instance of
     * {@link StandardServletAsyncWebRequest} gets created.
     *
     * @param request  the current request
     * @param response the current response
     * @return an AsyncWebRequest instance (never {@code null})
     */
    public static AsyncWebRequest createAsyncWebRequest(HttpServletRequest request, HttpServletResponse response) {
        return new StandardServletAsyncWebRequest(request, response);
    }

}
